Low Impedance Area Research Articles

A reliable fossa ovalis impedance mapping for safer transseptal puncture: A new vision beyond voltage.

Transseptal puncture (TSP) is widely used in clinical practice but is negatively affected by a nonneglectable rate of complications and X-ray exposure. To address these problems, we investigated whether or not impedance mapping could correctly identify fossa ovalis (FO) and safely guide TSP. Electroanatomic mapping was performed with CARTO 3 system version 7 and a ThermoCool® SmartTouch® mapping catheter was employed. In each patient, an impedance map and a bipolar voltage map of the whole interatrial septum were collected, acquiring at least 150 points with a contact force ≥2 g and using the pattern matching filter. Thirty-five patients were enrolled. A low impedance area was clearly identified in 34 of them. In 30 patients (88%), the FO was located in the low impedance area. The map was obtained in sinus rhythm in 17 cases (50%); in 15 of these (88%), the TSP site, the patent foramen ovale, or the FO tenting area fell inside the low impedance area. The same numbers were observed when mapping during atrial fibrillation. To the best of our knowledge, this is the first study that provides the reliability and reproducibility of impedance mapping in identifying FO, an affordable and feasible tool that could be potentially introduced into clinical practice.

Utility of Contact Impedance Mapping in Differentiating the Mechanism of Focal Atrial Tachycardia.

Contact impedance mapping can differentiate focal atrial tachyarrhythmias from macroreentry (atrial flutter) and localized reentry (atrioventricular nodal reentry tachycardia) by detecting different patterns of regional unipolar tissue impedance distribution. Specifically, focal atrial tachycardia (AT) is characterized by the finding of a contiguous low-impedance area (CLIA) adjacent to the site of origin, surrounded by normal tissue impedance levels. However, it remains unclear whether or not this finding could distinguish different mechanisms of focal AT. In the present study, we sought to determine whether impedance and voltage maps in patients with microreentrant AT differ from those created due to triggered activity. Consecutive patients undergoing electrophysiologic study and the ablation of AT were included. All patients underwent mapping and ablation procedures in a standard manner. Contact impedance and voltage maps were collected in the background and analyzed offline for comparison. A total of 50 patients with 75 focal ATs were studied and ablated, and the mechanism of AT (ie, triggered activity versus microreentry) was determined. The 41 ATs attributed to triggered activity in 30 patients all demonstrated a CLIA containing or adjacent to the successful ablation site, while the 34 ATs in the 20 patients attributed to microreentry demonstrated uniform impedance. In contrast, microreentrant AT patients were more likely to have scar located adjacent to the site of origin (88.9% versus 18.2%). Three-dimensional mapping employing both contact impedance mapping and voltage mapping can reliably identify the mechanism of focal AT.

073_16938-C4 Contiguous Low Impedance Areas are Associated with Outflow Tract and Non-Outflow Tract PVCs

Contact tissue impedance mapping (CTIM) can differentiate focal atrial tachycardia (AT) from macro-reentry e.g. atrial flutter, and localized reentry e.g. AVNRT, by identifying a contiguous low impedance area (CLIA) only in AT. We suspect that the CLIA is related to triggered activity as suggested

Performance of the Scattering Matrix Arc Detection System on the JET ITER-like ICRF antenna

Ion Cyclotron Radio Frequency (ICRF) antennas operating under high voltage to couple high power to fusion plasmas are at risk of electrical arcing. The standard Voltage Standing Wave Ratio (VSWR) system does not protect low impedance areas, which are used in antennas to achieve load tolerance to variations in plasma loading during Edge Localised Modes (ELMs). The Scattering Matrix Arc Detection System (SMAD) was designed to create additional protection for these areas, and 4 complete systems were implemented and tested on the ITER-like antenna (ILA) on JET. This paper describes the performance under relevant experimental conditions of load tolerance and/or high voltage and electrical arcing causing generator trip events.

Scattering-matrix arc detection on the JET ITER-like ICRH antenna

Operating ion cyclotron resonance heating (ICRH) antennas at high power density puts them at risk of arcing which reduces the coupled power to the plasma because the perturbed impedance match triggers the voltage standing wave ratio (VSWR) based generator trip system but even worse might damage the antenna beyond repair because of the arc's localised energy deposition. New antennas are designed to operate in a load tolerant way which creates low impedance zones that are especially at risk since the existing VSWR protection systems are less sensitive to arcs in these areas. To protect these low impedance areas, a new arc protection system referred as scattering matrix arc detection (SMAD) has been proposed. This paper describes the basic operating principle and implementation in hard- and software for the JET ITER-like antenna (ILA), with testbed and preliminary JET commissioning results.